Electric switch



March 7, 1944. L, PIERCE ELECTRIC SWITCH Filed Aug. 11, 1942 2 Sheets-Sheet l Y mP R v 0 Ne U m 1 W M a Q R? E S s E N n w Patented Mar. 7, 1944 Lawrence Pierce, Edgewood, Pa.,

assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application August 11, 1942, Serial No. 454,357

5 Claims.

My invention relates, generally, to electric switches and, more particularly, to enclosed switches of the type known as safety switches.

An object of my invention, generally stated, is to provide a simplified and improved safety switch which shall be simple and eflicient in operation and which may be economically manufactured and installed.

A more specific object of my invention is to reduce the overall dimensions of an enclosed safety switch of a predetermined rating.

Another object of my invention is to utilize bridging. contact members of the, double break type in an enclosed switch.

A further object of my invention is to control the movement of the arcs drawn between a movable bridging contact vmember and its cooperating stationary contact members.

Still another object of my invention isto prevent the separation of abutting contact members by a heavy overload current. r

Other objects of my invention will be eitplained fullyhereinafter or willbe apparent to those skilled in the art.

In accordance with one embodiment of my invention, bridging contact members of the double break type are so disposed between the fuses and the base or rear wall of the cabinet in which a switch is mounted that the overall length of the switch is materially shortened. Magnetic material is so disposed on the stationary contact mem bers that the arcs formed upon opening the switch are moved into a grid structure. The magnetic material also functions to prevent the contact members from blowing open while carrying a heavy overload current.

For a fuller understanding of the nature and objects of my invention, reference may be had to the following detailed description taken in conjunction with the accompanying drawings, in which:

Figure l is a view, in plan, of a switch structure embodying my invention, portions being cut away forclearness;

,Fig. 2 is a view, partially in elevation and partially in section, of the switch structure shown in Fig. 1, and a Fig. 3 is an enlarged detailed view showing a bridging contact member in a partially open positron.

Referring to the drawings, thegstructure shown therein comprises a cabinet l0, only a portion of which is shown, for enclosing a three-pole switch H. In accordance with the usual practice, the

cabinet l may be formed from sheet steel and a rotatable shaft (2 is provided for opening and closing the switch members. One end of the shaft I2 may extend through a side wall of the cabinet 10 and an operating handle (not shown) may be provided for actuating the shaft.

As illustrated in Fig, 2, each pole unit of the switch H comprises a pair of spaced stationary contact members l3 and I4 which are bridged by a movable contact member I5. The movable contact member i5 is resiliently mounted in a stirrup l6 which is carried by a bracket H secured to the shaft 12. The stirrup I5 is insulated from the bracket ll'by an insulating and supporting member i8. A spring I9 is disposed inside the stirrup 10 for maintaining a predetermined contact pressure when the bridging member I5 is actuated into engagement with the stationary contact members l3 and M by rotative movement of the shaft 12.

In order to extinguish quickly the arcs drawn between the stationary contact members l3 and I4 and the bridging member during the opening of the electrical circuit, an arc extinguishing device 2| is disposed adjacent the contact members l3 and I4 opposite the sides of the contact members engaged by the bridging member [5. The are extinguishing device 2| may comprise a plurality of spaced plates 22 which are mounted in an insulating support 23 that may be secured to the bottom or rear wall of the cabinet 10 by screws 20, see Fig. 1.

The insulating member 23 also supports the contact members I3 and M, the contact member [3 being secured to the insulating member 23 by a bolt 24 and the contact member I4 is secured by a bolt 25. An opening 26 is provided at the one end of the contact member M for making the necessary electrical connection when the switch is installed in service.

A fuse terminal 21 is also secured to the insulating member 23 by means of the bolt 24. A similar fuse terminal 28 is secured to an insulating support 29 by a bolt 3| which is similar to the bolt 24. The insulating support 29 may be mounted in a channel 32 which may be supported by the sides of the cabinet 10. The iuse terminals 21 and 23 may be of the type fully described in the copending application of Lawrence Pierce et al., Serial No. 332,046, filed April 27, 1940, now Patent No. 2,301,700 isued Nov. 10, 1942, and are designed to hold a fuse 33 securely in position when clamped in the terminals by means of pivoted arms 34 which are clamped against the fuse by cylindrical nuts 35 disposed on the ends of the bolts 24 and 3|. A conductor 39 having an open- I rent.

.disposed with respect to the arc streams between the contact members that the arcs are moved toward the magnetic members in the direction ing 31 therein, is provided for making an electrical connection to the fuse terminal 28.

It will be seen that the overall length of the switch unit I I is materially shortened by utilizing the bridging contact members and mounting the one fuse terminal directly on the arc extinguishing device 2| as illustrated. At the same time the necessary clearances between the switch parts are maintained for operating the switch at the usual voltages for which the switch is designed. In this manner the size of the cabinet and hence the space required for installing the switch are materially reduced.

In order to insure that the arcs drawn between the stationary contact members l3 and I4 and the bridging contact member 15 will be moved into the arc extinguishing device 2i, separate pieces of magnetic material 38 are provided on the sides of the contact members I3 and I4 opposite the sides engaged by the bridging member IS. The pieces of magnetic material 38 are disposed between the contact members l3 and I4 and theplates 22 of the arc extinguishing device 2!.

As illustrated in Fig. 3, an arc is drawn between the contact member l3 and the bridging contact member l5 and also between the contact member l4 and the bridging contact member l5 when the contact members are separated to interrupt a power circuit. As explained hereinbefore, the pieces of magnetic material 38 are so disposed on the back sides of the contact members l 3-and I4 that strong fields are produced on the outside of the arc streams which move the arc streams in the direction indicated by the arrows. Thus, the two arcs are united'into a single are between the contact members l3 and M which is then moved into the plates 22 of the arc extinguishing device 2|, thereby causing the arc to be extinguished in a manner ,Well known in the art.

1 The principle involved in the moving of the arc stream in the desired direction is similar to that of an electrical conductor being drawn toward any magnetic material placed in the vicinity of the conductor while carrying an electric cur- Thus, the magnetic members 38 are so causes the two streams to unite into a single stream flowing betweenthe contact members 13 and Id and then causes this stream to be drawn towards the arc extinguishing device 2|.

Furthermore, the magnetic members 38 carry a flux which encircles the bridging contact member I 5 while it is in engagement with the stationary members l3 and I4 and, consequently produces a strong pull on the bridging member IS in a direction to hold the contacts closed while conducting heavy currents and oppose the normal tendency of the contact members to be blown open against the force of the spring 19 during short circuit conditions. In this manner injury to the contact members is prevented during the interval required for the fuse 33 to clear the circuit when a fault condition occurs. Otherwise, no arcs drawn between the separated contact members might be of such intensity as to burn badly or even melt the contact members.

It will be understood that the moving of the V are in the manner hereinbefore described during normal operation of the switch reduces contact burning. If the arc does not move toward the center or should move outwardly instead of inwardly it will usually result in a short circuit between the poles of the arc boxes of a multipole switch, such as herein illustrated. The use of the magnetic material between the stationary contact members and the grid structure produces a magnetic field of sufficient strength to move the arc toward the center and into the de-ionizing grids.

From the foregoing description it is apparent that I have provided an enclosed switch structure which utilizes a bridging moving contact member of the double break type, thereby having the advantage of interrupting the power circuit at two points. Furthermore, the dimensions of the switch are materially reduced as compared with previous switches having the same rating as the present switch. In view of the simplicity of the parts and the smaller dimensions of the switch and cabinet the cost of manufacturing the switch may be materially reduced.

Since numerous changes may be made in the above described construction and different embodiments of the invention may be made without r departing from the spirit and scope thereof, it

' not in a limiting sense.

I claim as my invention:

1. In an electric switch, in combination, a pair of spaced stationary contact members, a bridging contact member for engaging and disengaging said stationary contact members to establish and interrupt an electric circuit therethrough, an arc extinguishing device disposed adjacent the stationary contact members, and a piece of magnetic material mounted on the side of each stationary contact member opposite the side engaged by the bridging member and disposed between the stationary contact members and the arc extinguishing device for. moving the arcs formed during the interruption of the circuit between said stationary contact members into said extinguishing device.

2. In an electric, switch, in combination, a pair of spaced stationary contact members, a bridging contact member for engaging and disengaging said stationary contact members to establish and interrupt an electric circuit therethrough, an arc extinguishing device disposed adjacent the side of the stationary contact members opposite the side engaged by the bridging member, and magnetic means mounted on the stationary contact members opposite the side engaged by the bridging member and disposed between the stationary contact members and the are extinguishing device for moving the, arcs formed during the interruption of the circuit between said stationary contact members'into said extinguishing device.

3. In an electric switch, in combination, a pair of spaced stationary contact membersa bridging contact member for engaging and disengaging said stationary contact members to establish and interrupt an electric circuit therethrough, an arc extinguishing device disposed adjacent the side of the stationary contact members opposite the side engaged by the bridging member, and a piece of magnetic material mounted on the side of each stationary contact member opposite the side engaged by the bridging member and disposed between each one of the stationary contact members and the arc extinguishing device for moving the arcs formed during the interruption oi the circuit between said stationary contact members into said extinguishing device.

4. In an electric switch, in combination, a pair of spaced stationary contact members, a springbiased contact member for bridging said stationary contact members to establish an electric circuit therethrough, and magnetic means mounted on each one of the stationary contact members and overlapping portions of the bridging contact member thereby carrying a flux which encircles the bridging contact member to oppose movement of the bridging contact member away from the stationary contact members while carrying current.

5. In an electric switch, in combination, a pair of spaced stationary contact members, a movable contact member for bridging said stationary contact members to establish an electric circuit therethrough, and a piece of magnetic material mounted on the side of each stationary contact member opposite the side engaged by the bridging member and overlapping a portion of the bridging member thereby carrying a flux which encircles the bridging member to oppose movement of the bridging member away from the stationary contact members while carrying current.

LAWRENCE PIERCE. 

